Radio hardenable powder paints

ABSTRACT

The invention relates to powder coating material curable with high-energy radiation, comprising an unsaturated polyester resin (A) and a polymeric crosslinker (B) containing, based on the polymer main chain, terminal and/or pendant propenyl, butenyl and/or isoprenyl groups. The unsaturated polyester resin (A) and/or the polymeric crosslinker (B) comprise structural units of the general formula I and/or II. These novel powder coating materials are curable with high-energy radiation, preferably UV light, and are notable in particular for a very good viscosity stability during the preparation, in the melt, of the resins and the compounding of the coating materials, for outstanding coating properties, and for a low oxygen sensitivity on curing. The films resulting after the cure, moreover, exhibit outstanding elasticity.

[0001] The invention relates to powder coating materials curable withhigh-energy radiation and to a method of coating substrate surfaces withsuch a powder coating material.

[0002] The coating of any substrates with radiation-curable powdercoating materials, preferably UV-curable powder coating materials, isgaining increasingly in interest. Advantages are expected from the factthat, in contrast to systems which cure by heat alone, there is atheoretical separation of the melting process and the curing reaction.

[0003] In the practical development of such UV powder coating materials,however, a series of problems have arisen. With the majority ofpolymers, these problems result substantially from the impossibility ofunifying the desired blocking resistance of the powders, on the onehand, and the required elasticity of the cured coating films, on theother. When the polymers which are the basis of the respective UV powdercoating material are formulated to be so hard that the resulting powdersare resistant to blocking, the coating films which result after curingare brittle.

[0004] The majority of known UV powder coating materials are based onpolymer systems containing acrylic and/or vinylic unsaturation. A greattechnical problem of these systems results from the risk of prematurethermally activated polymerization of the individual components duringtheir preparation and during the process of compounding to ready-to-usecoating materials, which generally takes place in a melt extruder. Aparticularly critical operation is the melting of the applied coatingsprior to radiation crosslinking. During this operation, the desire isfor temperatures as high as possible in order to achieve meltviscosities which are as low as possible. In the course of trials withknown acrylically unsaturated systems it was found that, owing to thispremature thermally activated polymerization, the hoped-for effect ofbetter leveling could not be achieved.

[0005] DE-A-31 07 450 disclosed unsaturated polyesters containingoligomers of cyclopentadiene as end groups, which in the form ofsolutions in ethylenically unsaturated monomers can be used to producemoldings and coatings. As such ethylenically unsaturated monomers itspecifies the customary copolymerizable vinyl monomers or monomermixtures, such as styrene, vinyltoluene, divinylbenzene, diallylphthalate, and methyl methacrylate, for example.

[0006] EP-A-0 101 585 discloses unsaturated polyester resins which aremodified by adding cyclopentadiene onto the double bond of the polyesterand are then dissolved in vinyl monomers.

[0007] In EP-A-0 585 742, unsaturated crystalline polyesters arecombined with acrylically unsaturated polyurethane acrylates in order toincrease the blocking resistance.

[0008] EP-A-0 636 669 describes powder coating mixtures comprisingunsaturated polyesters or acrylically unsaturated polyacrylates withcrosslinkers, especially polyurethane crosslinkers, that arefunctionalized with vinyl ethers, vinyl esters or (meth)acrylic esters.The examples of this document reveal only a mixture of a polyester witha vinyl ether urethane.

[0009] As a further document, WO 99/14254 describes combinations ofunsaturated polyesters or unsaturated polyacrylates with crosslinkers,preferably polyurethanes, that are functionalized with a(poly)isocyanate and vinyl ethers or unsaturated alcohols.

[0010] On the basis of this prior art, an object of the presentinvention was to provide powder coating materials curable withhigh-energy radiation, preferably UV light, which have sufficientthermal stability during application, i.e., during the melting process,in combination with a sufficient blocking-resistant hardness, but whichstill give elastic coating films after curing.

[0011] This object has been achieved by means of powder coatingmaterials comprising an unsaturated polyester resin (A) and a polymericcrosslinker (B) containing, based on the polymer main chain, terminaland/or pendant propenyl, butenyl and/or isoprenyl groups, saidunsaturated polyester resin (A) and/or said polymeric crosslinker (B)comprising structural units of the general formula I and/or II.

[0012] The novel powder coating materials of the invention are curablewith high-energy radiation, preferably UV light, and are notable inparticular for a very good viscosity stability during the preparation,in the melt, of the resins and the compounding of the coating materials,for outstanding coating properties, and for a low oxygen sensitivity oncuring, which takes place preferably from the melt. The films resultingafter the cure, moreover, exhibit outstanding elasticity.

[0013] In principle, the powder coating materials of the invention mayalso be cured by heat with initiators which in response to heat providefree radicals, such as peroxides, azo initiators or C-C labilecompounds. Particularly worthy of mention in this context is acombination of the two cited curing methods, which has also become knownby the term “dual curing”. In the case of dual cure, curing is first ofall carried out to a so-called B stage, i.e., a partly cured state, atwhich point curing is interrupted and is started again at a later pointin time by another mechanism.

[0014] The novel powder coating materials of the invention are notablefor improved leveling on application to the substrate that is coated.The dicyclopentadiene content of the powder coating materials results inextremely high UV reactivities. Moreover, the dicyclopentadiene-modifiedpolyesters are formulated for a sufficient blocking-resistant hardness.

[0015] The polyester resins (A) of the powder coating materials of theinvention consist of unsaturated polyester resins, known per se,containing structural units of the general formula I and/or II which arederived from dicyclopentadiene (DCPD). The polyester resins aresynthesized by methods already known in the prior art, generally bypolycondensation of polyfunctional hydroxyl compounds withpolyfunctional acids and/or their anhydrides at relatively hightemperatures. Moreover, it is often advantageous to start from theesters of such compounds and to obtain the polyesters bytransesterification at relatively high temperatures, since suchtransesterifications may proceed more readily and more rapidly than thedirect esterification. The unsaturated nature of the polyesters comesabout through the (additional) use of unsaturated compounds in the acidcomponent and/or unsaturated alcohol components, such as alkenediolsand/or oxalkylated alkenediols, for example. Preferably, unsaturatedpolyester resins are obtained with maleic acid and/or maleic anhydrideand/or fumaric acid, since these compounds are available industriallyand are inexpensive. Furthermore, polyesters containing amide structuresmay be obtained by the (additional) use of polyfunctional amines. Theadditional use of monofunctional starting materials is also possible inorder, for example, to regulate the molecular weight. Below, examplesare given of compounds suitable for synthesizing the polyester resins.

[0016] Examples of suitable compounds of this kind are:

[0017] adipic acid, suberic acid, phthalic acid isomers,tetrahydrophthalic acid, endomethylenetetrahydrophthalic acid,hexahydrophthalic acid, fumaric acid, maleic acid, itaconic acid,citraconic acid, trimellitic acid, pyromellitic acid, ethylene glycol,polyethylene glycol, propylene glycol, polypropylene glycols, butanediolisomers, hexanediol, neopentyl glycol, trimethylolpropane, glycerol,pentaerythritol, bisphenol A, hydrogenated bisphenol A,OH-polyfunctional polymers, such as hydroxyl-modified polybutadienes orhydroxyl-bearing polyurethane prepolymers and epoxy resins,polyfunctional natural substances or derivatives thereof, such aslinseed oil fatty acid, dimeric and polymeric linseed oil fatty acid,castor oil, and castor oil fatty acid. In addition to the compoundsexemplified, the hydroxyl compounds specified later on below in thecontext of the polymeric crosslinker (B) are also suitable forsynthesizing the polyesters. The introduction of amide and imidestructures into polyester resins is known, for example, from DE-A-15 700273 and DE-A-17 200 323. Such polyesteramides or polyesterimides maymeet particular requirements—regarding the heat resistance, forexample—in many cases more effectively than straight polyesters.

[0018] The structural units of the general formula I and/or II are ineach case introduced preferably by way of adducts of dicyclopentadieneor its oligomers with α,β-unsaturated carboxylic acids or theiranhydrides. Very readily available are the adducts of maleic anhydrideand water with DCPD in accordance with the general formula III and/or IV

[0019] Additionally to the unsaturated polyester resin, the polymericcrosslinker (B) may comprise saturated polyesters having structuralunits of the general formula I and/or II. These may have beenintroduced, for example, by way of dihydrodicyclopentadienol inaccordance with the general formula V.

[0020] In one preferred embodiment of the powder coating materials ofthe invention, the crosslinker (B) comprises polymers selected frompolyesters, polyurethanes and mixtures thereof. In this case it ispreferred for the crosslinker to comprise terminal and/or pendantisoprenyl groups, preferably 3-methyl-3-butene.

[0021] Polyurethanes containing isoprenyl groups are obtained, forexample, by the (additional) use of the commercially availableisopentenols (isoprenols) 2-methyl-3-buten-2-ol, 2-methyl-2-buten-1-ol,and, preferably, 3-methyl-3-buten-1-ol. The polymer main chain of thecrosslinker may be linear, branched as desired, or dentrimeric incomposition. In the polymer main chain as well, purely C—C-linkedcompounds and compounds containing ether groups in the chain arepossible. Methods of preparing 1-propenyl ethers are given, for example,by J. V. Crivello et al. in Macromolecular Engineering, Plenum Press,New York, 1995. Available commercially are propenyl ethers of polyols,such as 1,6-di(1-propenoxy)decane or tetraethylene glycol di(1-propenylether). Also available are isopropenylbenzyl-m-isopropyl isocyanate,1-propenyl glycidyl ether, and isoprenol (3-methyl-3-buten-1-ol).Polyurethanes containing allyl and/or crotyl groups terminally may beconverted into propenyl or butenyl groups by additionally using allylalcohol or crotyl alcohol, respectively, with rutenium catalysts, forexample (Crivello, Pol. Mat. Sc. And Eng. 1995, Vol. 72, page 473).

[0022] Using the abovementioned isocyanates, glycidyl ethers, andisoprenol it is possible to synthesize terminally functionalizedpolymers. Isoprenol is preferred in this context since it brings aboutvery good UV reactivity together with the unsaturated polyester resin(A) and is available at favorable cost commercially.

[0023] In principle, all polyurethanes and polyesters which may beprepared in accordance with the commonly known rules are suitable forsynthesizing the crosslinkers (B). Preference is given to polyurethanesmade from isocyanates and compounds reactive with them, such as hydroxylcompounds, or polyfunctional hydroxyl compounds, with particularpreference in combination with isoprenol.

[0024] Prepolymeric polyesters for synthesizing the crosslinkers (B) areobtained in principle as stated for the unsaturated polyester resins(A). The reactive termination may be achieved, for example, by theadditional use of isopropenyl-benzyl-m-isopropyl isocyanate, 1-propenylglycidyl ether, and isoprenol. Also of particular significance inconnection with the synthesis of the crosslinkers (B) are oligomericand/or polymeric substances, preferably polyhydroxyl compounds, such aspolyetherpolyols, ethoxylated and/or propoxylated hydroxyl compounds,and polytetrahydrofurans, for example. The additional use ofpolyesterpolyols, e.g., those of the polycaprolactone type, result incoatings of particularly good weathering stability, flexibility,adhesion, chemical resistance, and high yellowing resistance. Also ofsignificance are cycloaliphatic and araliphatic hydroxyl compounds, suchas hydrogenated bisphenol A, bisphenol A and compounds derived frombisphenol A, for example, such as bisphenol-A-dialkanols. In the contextof the synthesis of the polyurethanes used for the crosslinkers (B), theadditional use of melamine results in substances which crystallizeparticularly well and which, as trifunctional crosslinkers, give rise tohighly crosslinked coatings having particularly good mechanicalproperties, such as scratch resistance and abrasion resistance.

[0025] Suitable isocyanates for synthesizing the polymeric crosslinkers(B) with the (additional) use of polyurethanes are all known substancescontaining on average more than one isocyanate group, examples beingaliphatic, cycloaliphatic and/or aromatic isocyanates. Also ofparticular interest are polymerized isocyanates, based for example onhexamethylene diisocyanate or isophorone diisocyanate. Here again, theselection may be made in accordance with criteria known to the skilledworker in the field of urethanes. For example, aliphatic and/orcycloaliphatic isocyanates, such as hexamethylene diisocyanate orisophorone diisocyanate (IPDI), result in particularlyweathering-resistant, yellowing-free and chemical-resistant coatings,whereas aromatic isocyanates, such as 4,4′-methylenedi(phenylisocyanate) (MDI) and toluene diisocyanate (TDI), give coatings whichhave particularly good mechanical properties but which tend to yellowunder the effect of light. A further selection criterion is the price.For coatings where the color is not important, for example, the cheaperMDI may be preferred over the more expensive IPDI.

[0026] By way of the structure of the crosslinkers (B) it is possiblewithin a wide range to determine the end properties of the curedcoatings. Linear crosslinkers with only terminal and no pendant reactivegroups result in a relatively wide-meshed crosslinking with a relativelylarge network are length and relatively high flexibility of the curedcompositions. Highly branched crosslinkers and/or those with a highdegree of pendant functionalization give high crosslinking densities andhard or else brittle coatings. The hardness or flexibility depends, ofcourse, not only on the nature of the crosslinker (B) but also on thestructure of the unsaturated polyester resin (A).

[0027] The special measures required for the synthesis of theunsaturated polyesters (A) of the powder coatings of the invention, withregard to the requirements relating, for example, to the hardness,elasticity, viscosity, and softening point, are taken in accordance withrules known to the skilled worker. For example, the elasticity of thecured polyester resins may be varied through the chain length of thepolycarboxylic acids or polyols used. Polyester resins synthesized withethylene glycol, butanediol, hexanediol or adipic acid have a greaterflexibility than, say, those based on neopentyl glycol or phthalic acid.Moreover, the properties of the unsaturated polyesters (A) may becontrolled through the additional use of polyfunctional compounds, whichgenerate branches in the polyester molecules. Examples of suchpolyfunctional compounds are trimellitic acid or trimethylolpropane.

[0028] In one preferred embodiment, the unsaturated polyesters (A)and/or the crosslinker (B) are made crystalline or partiallycrystalline, since when this is the case the resulting polymers aregenerally blocking resistant even at low molecular weight, and suchpolymers give rise to low-viscosity melts and coatings with particularlygood leveling. The rules in accordance with which crystallinity may bebrought about in polymers are known per se to the skilled worker.Crystallinity or partial crystallinity may be produced in polyurethanesor polyesters, for example, by additionally using linear compoundshaving an even number of carbons, such as glycol, butanediol,hexanediol, hexamethylene diisocyanate.

[0029] The molecular weight distribution as well influences the blockingresistance and melt viscosity. A narrow molecular weight distribution isfavorable in the range of low molecular weights, i.e., in the oligomerrange, where a distribution from 500 to 5000 is typical. Suitablemeasures for adjusting the molecular weight and establishing a desiredmolecular weight distribution in unsaturated polyester resins andpolyurethanes are known per se.

[0030] The unsaturated polyesters (A) and/or the polymeric crosslinker(B) may, however, also be amorphous. In that case they are preferablyselected in each case so as to have a Tg>50° C., with particularpreference >80° C.

[0031] Where crystalline and amorphous compounds are combined, it ispossible, for example, for the polymeric crosslinker to be crystallineand to have a low molecular weight, so that it polymerizes even at a lowmelting point. As unsaturated polyesters (A), amorphous compounds with ahigh Tg, as already mentioned earlier on above, are suitable in thatcase.

[0032] By this combination as well it is possible to prepare powdercoating materials having a sufficient blocking-resistant hardness.

[0033] The powder coating materials of the invention may furthercomprise additives selected from curing accelerators, photoinitiators,light stabilizers, pigments, fillers, compounds which when exposured toheat form free radicals, further customary additives, and any desiredmixtures thereof.

[0034] Suitable photoinitiators include known, commercially customarycompounds; preferably, the photoinitiators used have a low volatility atthe melting temperature of the coating materials. Given an appropriateselection of photoinitiator it is also possible to obtain pigmented UVcoating materials. A particularly high UV reactivity is displayed bythose compounds which have H-acceptor groups attached chemically to thepolyester (A) and/or the crosslinker (B). Compounds of this kind may beobtained by the additional use of reactive phenone compounds, such ashydroxybenzophenone, bishydroxybenzophenone or benzophenonecarboxylicacids and/or their anhydrides.

[0035] The invention also relates to a method of coating substratesurfaces with the powder coating material of the invention. Said methodcomprises applying the powder coating material to the substrate, meltingit thereon by application of heat, preferably by exposure to NIR light,and then curing it in the melt, in the course of cooling or aftercooling, by exposing it to high-energy radiation.

[0036] Suitable substrates include a very wide variety of materials,such as wood, plastics, woodbase materials, metal, stone, and precoatedsubstrates.

[0037] The method of the invention may be modified such that thesubstrate surface is coated with the powder coating material of theinvention which comprises compounds which on exposure to heat form freeradicals, curing being brought about with a combination of heat andhigh-energy radiation. By this means in particular it is possible tocarry out a two-stage cure which, as already mentioned earlier on above,is known by the term “dual curing”. In this case, for example, thermalcuring is carried out first of all, as a result of which the appliedpowder coating material on the substrate is crosslinked to a part-curedstate, before being caused to cure fully at a later point in time bycuring with high-energy radiation. If desired, the method may also becarried out in reverse order, with partial crosslinking with high-energyradiation being carried out first before the powder coating material iscured to completion, subsequently, by heat. Besides thermal curing, anyother curing mechanisms may be combined with the curing by means ofhigh-energy radiation.

[0038] In the text below, the invention will be illustrated withreference to implementation examples.

EXAMPLES

[0039] Compound I (Monocarboxylic Acid of Formula III)

[0040] A stirring flask with heating and reflux condenser is chargedwith 710.81 g of 93% dicyclopentadiene (5.0 mol) 490.30 g of maleicanhydride (5.0 mol).

[0041] The mixture is heated to 125° C. under a gentle stream ofnitrogen and then 95.00 g of water (5.0 mol + 5 g)

[0042] are added from a dropping funnel over the course of one hour andthe mixture is left to react at 125° C. for one hour. A monocarboxylicacid of formula V is formed.

Example 1 Polyester (A)

[0043] A stirring flask with heating and top-mounted distillation unitis charged with 1033.60 g of compound 1 (4.0 mol)  235.20 g of maleicanhydridyl ether (2.4 mol)  278.40 g of fumaric acid (2.4 mol) 1344.00 gof dicyclohexanolpropane (5.6 mol)  630.00 g of polyol TP 70 (1.4 mol)  4.00 g of Fascat 4201 (esterification catalyst)   0.50 g ofhydroquinone.

[0044] The mixture is heated rapidly to 130° C. under a gentle stream ofnitrogen. Then the temperature is raised gradually to 190° C. over thecourse of 4½ hours, during which the water of condensation which formsis removed by distillation. The resulting resin melt is poured out ontoaluminum foil, and solidifies on cooling. The polyester has an acidnumber of 12 and a viscosity of 48 Pas/130° C. and 31 Pas/140° C. It isreadily grindable, and the powders are blocking resistant.

Example 2 Isoprenol-Terminated Crosslinker (B) with CopolymericallyAttached Photo Initiator

[0045] A stirring flask with heating and reflux condenser is chargedwith   1000 g of ethyl acetate 123.84 g of hexamethylene diisocyanate 32.00 g of tolylene diisocyanate  0.30 g of hydroquinone monomethylether and at about 60° C.  27.00 g of 1,4-butanediol  11.80 g oftrimethylolpropane  39.60 g of 4-hydroxybenzophenone  68.90 g ofisoprenol (3-methylbut-3-en-1-ol)

[0046] are run in together over the course of 40 minutes. Stirring iscontinued at about 60° C. for 2 hours, after which the mixture is cooledand the precipitate formed is filtered off and dried. This gives 285 gof a white powder having a softening range of from 82 to 97° C. and aviscosity of 1077 mPas at 130° C.

Example 3 Isoprenol-Terminated Crosslinker (B)

[0047] A stirring flask with heating and reflux condenser is chargedwith   1000 g of ethyl acetate 123.84 g of hexamethylene diisocyanate 32.00 g of tolylene diisocyanate  0.30 g of hydroquinone monomethylether and at about 60° C.  36.00 g of 1,4-butanediol  11.80 g oftrimethylolpropane  68.90 g of isoprenol (3-methylbut-3-en-1-ol)

Example 4 Isoprenol-Terminated Crosslinker (B) with Polycaprolactone

[0048] A stirring flask with heating and reflux condenser is chargedwith   1000 g of ethyl acetate 123.84 g of hexamethylene diisocyanate 32.00 g of tolylene diisocyanate  0.30 g of hydroquinone monomethylether and at about 60° C.  31.50 g of 1,4-butanediol  11.80 g oftrimethylolpropane  23.00 g of Capa 200 (polycaprolation, Solvay)  68.90g of isoprenol (3-methylbut-3-en-1-ol)

[0049] Preparation of Powder Coating Samples The constituents listed intable 1 are weighed out into a small stirring flask, melted at 120° C.in an oil bath under nitrogen, and mixed for 5 minutes. The melts arethen poured out onto aluminum foils and left to cool. In all cases thisgives hard resins, which were ground in a laboratory mill and sieved toa particle size of <40 μm. The sample with the crosslinker according toExample 4 was grindable only following the addition of a little dry ice.All of the powders, however, were blocking resistant on room temperaturestorage. Comparative example with VP 1 (Alftalat VAN 1743, commercialunsaturated paint polyester without DCPD groups) TABLE 1 powder coatingmaterials used Ex. Crosslinker Darocure No. Polyester (A) (B) 2954Characterization 1. 75 g VP1 25 g VB2 — (A) without DCPD (B) withphotoinitiator groups 2. 75 g VP1 25 g VB2 3 g 3. 75 g VP1 25 g VB3 3 g(A) without DCPD (B) without photoinitiator groups 4. 75 g VP1 25 g VB43 g (A) without DCPD (B) without photoinitiator groups with Capa 5. 75 gPA1 25 g VB2 — (A) with DCPD (B) with photoinitiator groups 6. 75 g PA125 g VB2 3 g 7. 75 g PA1 25 g VB3 — (A) with DCPD (B) withoutphotoinitiator groups 8. 75 g PA1 25 g VB4 — (A) with DCPD (B) withoutphotoinitiator groups with Capa

[0050] Testing the Examples for Curability and Film Quality

[0051] The coating powders were applied through a sieve to cleanedbright metal deep-drawing panels in an amount sufficient to give, aftercuring, films with a thickness of approximately 65-75 μm. The tests wereconducted on verified coating areas of the sample panels that were ofcomparable thickness. The sample panels were subjected to melting for 3minutes on an adjustable hot plate preheated to 140° C., then the slideshutter of a preheated mercury vapor lamp (Hönle UV 400, emissionmaximum approximately 365 nm, energy density 38 mW/cm2) was opened forthe stated time, then closed again, and the panels were removed from thehot plate. The tests were carried out following storage overnight atroom temperature. The results are given in Table 2. TABLE 2 Test resultsEx- po- sure Ex. time No. [s] AC* ESP* PH* CC* Comments 1. 10 sol.* <0.556 5 Without DCPD in (A), with 20 5 <0.5 51 5 photoinitiator (Fi) in(B): UV- 60 10 <0.5 82 5 curable with low reactivity 2. 10 sol.* <0.5 645 Without DCPD in (A), with 20 10 <0.5 78 5 (Fi) in (B): and with added60 45 1.5 138 5 photoinitiator: better UV- 3. 10 sol.* <0.5 93 5 WithoutDCPD in (A), no (Fi) 20 5 <0.5 97 5 in (B), with added Fi: UV- 60 25 1.5122 4 curable with moderate reactivity 4. 10 30 2.5 81 4 Without DCPD in(A), no (Fi) 20 60 3.5 97 4 in (B), Capa in (B) with added 60 >100 2.8129 3 Fi: UV-curable with moderate reactivity, better adhesion 5. 10 802.8 193 4 DCPD in (A), no (Fi) in (B): 20 >100 3.5 194 4 UV-curable inaccordance 60 >100 3.0 192 3 with the invention with very highreactivity 6. 10 >100 2.5 194 4 DCPD in (A), no (Fi) in (B): 20 >100 2.1196 4 with added Fi: UV-curable in 60 >100 3.5 193 4 accordance with theinvention with very high reactivity 7. 10 >100 2.2 193 4 DCPD in (A),without (Fi) in 20 >100 3.1 201 4 (B): with added Fi: UV- 60 >100 3.2198 3 curable in accordance with the invention with very high reactivity8. 10 >100 5.2 193 2 DCPD in (A), without (Fi) in 20 >100 7.1 201 0 (B)with Capa in (B) with 60 >100 7.2 198 0 added Fi: UV-curable inaccordance with the invention with very high reactivity, very goodadhesion and elasticity

What is claimed is:
 1. A powder coating material curable withhigh-energy radiation, comprising an unsaturated polyester resin (A) anda polymeric crosslinker (B) containing, based on the polymer main chain,terminal and/or pendant propenyl, butenyl and/or isoprenyl groups, saidunsaturated polyester resin (A) and/or said polymeric crosslinker (B)comprising structural units of the general formula I and/or II.


2. The powder coating material as claimed in claim 1, wherein thestructural units of the general formula I and/or II have been introducedby way of adducts of dicyclopentadiene or its oligomers withα,β-unsaturated carboxylic acids or their anhydrides.
 3. The powdercoating material as claimed in claim 1 or 2, wherein the structuralunits of the general formula I and/or II have been introduced by way ofadducts of dicyclopentadiene or its oligomers with maleic anhydride inaccordance with the general formula III and/or IV.


4. The powder coating material as claimed in any of claims 1 to 3,wherein additionally to the unsaturated polyester resin the crosslinker(B) comprises saturated polyesters having structural units of thegeneral formula I and/or II.
 5. The powder coating material as claimedin claim 4, wherein the structural units of the general formula I and/orII have been introduced into the saturated polyesters by way of acompound of the general formula V.


6. The powder coating material as claimed in any of claims 1 to 5,wherein the crosslinker (B) comprises polymers selected from polyesters,polyurethanes and mixtures thereof.
 7. The powder coating material asclaimed in claim 6, wherein the crosslinker (B) comprises terminaland/or pendant isoprenyl groups, preferably 3-methyl-3-butene.
 8. Thepowder coating material as claimed in any of claims 1 to 7, furthercomprising additives selected from curing accelerators, photoinitiators,light stabilizers, pigments, fillers, compounds which when exposed toheat form free radicals, further customary additives, and mixturesthereof.
 9. The powder coating material as claimed in claim 8,comprising photoinitiators attached chemically to the polyester resin(A) and/or the crosslinker (B).
 10. A method of coating substratesurfaces with a powder coating material as claimed in any of claims 1 to9, which comprises applying said powder coating material to thesubstrate, melting it thereon by application of heat, preferably byexposure to NIR light, and then curing it in the melt, in the course ofcooling or after cooling, by exposing it to high-energy radiation. 11.The method as claimed in claim 10, wherein the substrate surface iscoated with a powder coating material as claimed in claim 8 or 9 whichcomprises compounds which on exposure to heat form free radicals, curingbeing brought about with a combination of heat and high-energyradiation.
 12. The method as claimed in claim 11, comprising a two-stagecure in which the powder coating material is crosslinked to a part-curedstate by thermal curing and at a later point in time is cured tocompletion with high-energy radiation.
 13. The method as claimed inclaim 12, comprising firstly partial crosslinking with high-energyradiation and subsequent curing to completion by heat.